Elastic fluid turbine



Margh 16, 1943; 'J. K. SALISBURY 2,314,289

ELASTIC FLUID TURBINE Filed May 24, 1941 Qwm In e or: J. Kenne 'sbur-y, b y V I Q His Attorney.

Patented Mar. 16, 1943 UNITED STATES zone-ice John Kenneth": Salisbury, Schenectady; tssignor to-General Electric Company, a corporation of New York I Application May24, 1941, -Serial-'No$95il73 Claims.

The present invention -relates' to elastic fluid turbines comprising arotorwith a plurality, of bucket wheels disposed in acasing and a plurality of diaphragms supported onthe casing and'a'ssociated with the bucket wheels toconduct elastic fluid thereto. Eachbucketwheel usually'has a. disk or supporting member and a row of buckets secured thereto and forming bucket passages between them. During operation'elastic'fiuidis directed by the diaphragms into the passages formed between adjacent buckets of the wheels whereby part of its energy is converted 'into mechanical energy and imparted to the wheel. In order'to increasethe efficiency'of tu'rbinesit isthe practice to provide each bucket wheel with a shroudband connecting the tips of the buckets and having asealing edge in cooperative relation with the outer ring of a diaphragm to reduce bucket tip losses, that is, leakage of fluid around the tips'of the buckets. The objectof myinvention'is to. provide an improved construction and arrangement of elastic 'fluid turbines of the kind described above whereby loss 'due to leakage of elastic fluid around the tips of the buckets is 'further reduced. This is accomplished in accordance with my invention by the provision of sealing means which. in a preferred embodiment comprises a plurality of overlapping flexible sealing strips having portions secured to the outer ends of the buckets or to the shroudband'and other portions witha sealing edge in cooperative relation with an adjacent stationary member such as a diaphragm and arranged to be forced outwardto- Wards such member by the action of centrifugal force. An arrangement of this kind offers increasing resistance to flow: of leakage fiuidwith increase in speed of the-turbine. This is particularly desirable because of the increasing tendency for leakage withincreasing speed.

For abetter understanding of what I believe to be novel and my invention, attention is directed to the following description and the claims appendedthereto in connection with the accompanyin drawing.

In the drawing Fig. 1 illustrates a sectional view, partly broken away, oi an elastic fluid turbine embodying my invention; Fig. 2 is a View along lines 22 of Fig. 1; Fig. 3 is an enlarged perspectiveview of a-partof Figs. 1 and 2; and

v Fig. 4 illustrates a modification according to my invention.

The elastic fluid turbine as shown in the drawing has a casing ii]. A rotor with a bucket wheel l I having arrow .o'f"'buckets' l 2 is 'dis'pos'e'din the casing. Diaphragms l 3and"l 4 are "provided on each side ofthet bucketw'h'eehl l and supported oni'th'e casingil'll. Each diaphragm hasa 'rowof partitions 'l 5 "securedbetween"aninner disk 1'6 and I an outer ring Hand forming "a pluralitybf nozzles between them; During'ope'ration elastic fluid "is" direcfied'iby "the "nozzles formed between thejpartitions I 5t'0 the passages defined between the? buckets" 'I and dis chargedrrom' thelatt B1 to the; nozzlesbfthe diaphragm I14. I

Eachdoflcket I 2''haslanf' outer p'ortiorfwith "a ten'on lfi. 'A""shrolidband"l9 "is secured to"the tenons l 8"130 "confine the" -elastic ffll'lid within the passages formed "between the buckets. The shroudbah'dl'il, as'show'nii'n the pr sentexampie, maybeprovidedwith a'sea1in'ged e'2 0' in proximityto" the outer-rin "of "the diaphragm l'3 *to reduce leakage 'o ffluid' dischargedfiom thediaphra'gm I 3 around the outer "surface "of the shroudba'nd "19",0'1, "from answer viewpoint; 3 to reduce the bypassing" of fluid between the dia phragms I 3 and 14 "around the outerportiodo'f the bucketwheYH.

' As a further 'means'to reduce 'leakagebfflifid aroundth'e "buckerwneei, that "is," to reduce" tip loss, I provide in. accordance with my "invention flei'zible sealing meansisecured' to" the-outer portion of the bucket wheelinrocper'ative' relation with an "a'dj acent stationary memben'an'dlofiering increased 'r'e stanceto'fiow ofLlakagefiuid in response lid-increasing tuibine L'S'p'edJ #This sealing means in" alpife'r're'd Teii'ibodiihenhIas shown in "the "dl'awihg cbifipiises' 2i; plurality of overlapping sealing strips 2f prereramymade from 'a'soft metal." Each sealing stripThas' a 'portion 22" engagin the outer surfaceoftne shroudband I 9 "and'secured'to a .te'nori" rs by. awe'ld 23. Each seaung strip z I .has' 'anotl'i'er fl por'tibn '24 wincn'is' 'inelined'toward' a radial 'pIane .of the bucket vvh'eelfth'at "ifsf'toward' s 'the plaln'dfibtation of the". wheel; and 'hasasealing' edge :25 in proximity "to. a staticnary member.

In. thepresent fexampl. the outei' 'fin s of T the diaphragm "have" ahhularfpi'djctions' 2 6' "surroundingith bucket"wneei and forming moisture-collecting groove "orfgrooves i2l. v The :sealing edges 2 5" of 'the1stiips 2 l "are arranged in cooperative relation "with the inner cylindrical sealing surface dftheiprojectiodz'l' on'the outer d'iaphragmring I'l. Durin "operation centrifugal action forces the portions 24 of the sealing strips outward in radial direction whereby the sealing edges 25 are brought closer to the cylindrical sealing surface on the projection 21 and therefore offer an increased resistance to flow of leakage around the bucket wheel.

The arrangement shown in Fig. 4 comprises a turbine casing 30 and a diaphragm 31 with an outer ring 32 supported on the casing. A bucket wheel 33 is cooperatively associated with the diaphragm 3| and has a plurality of buckets 34 with outer ends connected by a shroudband 35. In order to reduce leakage of fluid around the outer surface of the shroudband 35, that is, around the tips of the buckets, especially at high turbine speed, a sealing strip 36 is provided. This strip has an inner portion securely fastened to the shroudband 35 by a weld 31. An outer portion of the sealing strip has a sealing edge 38 adjacent a sealing surface 39 formed by the casing 30. The sealing strip has a circumferentially corrugated portion 49. This portion permits the strip to be expanded radially at high speed by the action of centrifugal force whereby the clearance formed between the sealing edge 38 and the sealing surface 39 is reduced with increasing speed.

The invention is-especially important in connection with reaction turbine blading. The reactionwhich exists in a given stage increases with increasing speed. This increasing reaction causes an increasing pressure drop across the buckets and therefore an increased tendency of the elastic fluid to bypass the bucket wheel because the pressure drop across the bucket also exists between the inlet and outlet edges of the shroudband, that is, across the tips of the buckets. The centrifugal sealing device as described above has the advantage of sealing the space between the tips of the buckets and the adjacent stationary'elements at high speeds. The sealing device forms a small clearance at high speed and a larger clearance at low speeds. This large clearance at low speed is desirable especially in the case of turbines which are. frequently shut down because with a large clearance anydeflection due to non-uniform cooling or heating of the rotor will not permit of rubbing between the rotor and the stationary elements during the starting operation.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

Elastic fluid turbine comprising a casing member, a diaphragm member disposed within and supported on the casing member and forming an inner cylindrical sealing surface, a rotor having a bucket wheel with a row of buckets cooperatively associated with the diaphragm member, and sealing means to reduce leakage of fluid around the tips of the buckets, said sealing means comprising a plurality of sealing strips each having a portion secured to an outer portion of the bucket wheel and a flexible portion inclined to the radial plane of the bucket and with an outer sealing edge in proximity to said sealing surface.

2. Elastic fluid turbine comprising a casing member, a rotor with a bucket wheel having a plurality of buckets disposed within the casing member, diaphragm members on opposite sides of the bucket wheel and supported on the casing member, and sealing means to reduce leakage member, and means to reduce leakage around the between the diaphragm members around the outer tips of the buckets comprising a plurality of overlapping sealing strips secured to outer portions of the bucket wheel, one of the diaphragm members having a lateral projection concentrically surrounding the strips, each strip having a flexible portion with a sealing edge in cooperative relation with the projection and arranged to be forced outward towards the projection by the action of centrifugal force to increase the resistance to leakage flow with increasing speed of the bucket wheel.

3. Elastic fluid turbine comprising a casing, a rotor with a row of buckets disposed within the casing, a diaphragm on each side of the buckets and having a cylindrical projection surrounding the buckets and forming a moisture-collecting groove, and sealing means to reduce leakage of elastic fluid around the tips of the buckets comprising a shroudband secured to the tips of the buckets and having a sealing edge in proximity to a diaphragm and a plurality of circumferentially spaced overlapping sealing strips located concentrically within the projection, each strip having a portion secured to the shroudband and another flexible portion inclined towards the plane of rotation of the buckets and with a sealing edge in cooperative relation with the inner cylindrical surface of the projection, said other portion being arranged to be forced outward towards the cylindrical surface by the action of centrifugal force to offer an increasing resistance sealing surface, a bucket wheel having a row of buckets disposed within the casing member and cooperatively associated with the diaphragm tips of the buckets comprising a sealing strip secured to the outer portion of the bucket wheel and having a portion with a sealing edge in proximity to and surrounded by said sealing surface,

- said portion being circumferentially corrugated to cause the sealing edge to be forced closer to the sealing surface at high turbine speed.

5. Elastic fluid turbine comprising a casing, a diaphragm having an outer ring with a cylindrical projection supported on the casing, a bucket wheel with a row of buckets disposed within the casing and arranged to receive elastic fluid from the diaphragm, and means to reduce leakage of fluid around the tips of the buckets comprising a shroudband attached to the tips of the buckets and having a sealing edge in close proximity to said ring and a plurality of sealing strips, each strip having a portion engaging the shroudband and secured to an outer portion of a bucket and another flexible portion concentrically surrounded by said projection and inclined towards the plane of rotation with a sealing edge in proximity to the inner surface of the cylindrical projection, said other portion being flexible and adapted to be forced outward with increasing speed towards said cylindrical sealing surface in order to increase the restriction to leakage flow around the tips of the buckets with increasing speed of the turbine.

J. KENNETH SALISBURY. 

